Method for forming fine concavo-convex patterns, method for producing optical diffraction structure, and method for copying optical diffraction structure

ABSTRACT

A method for forming fine concavo-convex patterns by using a relief formation material  3  having a relief formation layer  2  composed of a resin having thermoplasticity and a relief pattern sheet  6  having on a surface thereof fine concavo-convex patterns  5 , wherein a photothermal conversion layer  7  is formed in the relief formation material  3  or the relief pattern sheet  6 ; the photothermal conversion layer  7  is irradiated with light  8  to make the photothermal conversion layer  7  generate heat in the state that the relief formation layer  2  is brought into contact with the fine concavo-convex patterns  5 ; and the fine concavo-convex patterns  5  are formed on the relief formation layer  2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for forming fineconcavo-convex patterns in which relief holograms and diffractionlattices are recorded, a method for producing an optical diffractionstructure composed of fine concavo-convex patterns, and a method forcopying an optical diffraction structure.

2. Description of Related Art

Relief holograms and diffraction lattices are for recording interferencefringes formed by interfering laser beams in form of fine concavo-convexpatterns. The fine concavo-convex patterns are composed of severalhundred to thousand fine projections in every 1 mm length.

In the case of copying the fine concavo-convex patterns, a copying formeis produced from a master hologram in which the interference fringes oflaser beams are directly recorded and the concavo-convex patterns of thecopying forme are transferred to a resin material to copy the fineconcavo-convex patterns by mass production.

In a conventional case of forming a copying forme from a masterhologram, it has been known to employ a method for producing diffractionpatterns of phase diffraction lattices, phase holograms and the like bystamping the patterns in a thermoplastic resin with a casting die (amother die) by pressure and heat. However, since formation of such planepatterns involves formations of a large number of phase diffractionlattices by repeating stamping many times in the thermoplastic resin andaccordingly raised parts are generated in the boundary regions betweenthe parts which are heated and pressurized and parts which are neitherheated nor pressurized, it becomes difficult to arrange the patternswithout any joining parts. Further, since the casting die is made of ametal, it has a high heat capacity and therefore, there occurs a problemthat the previously stamped and neighboring patterns are forciblyeliminated in the peripheral region where stamping is carried out newly.

There is a method for forming fine concavo-convex patterns sharp in thestamping circumferential region without any raised parts to be obstaclesby stamping a predetermined region in a simple manner so as to solve theabove-mentioned disadvantages (reference to Japanese Patent ApplicationLaid-Open No. 61-20723).

This method for forming a fine concavo-convex pattern is a method forforming concavo-convex patterns by stamping a predetermined surface areaof a casting die having fine concavo-convex patterns to a thermoplasticresin and is carried out by heating approximately point-likegeneratrices of the thermoplastic resin at the focal point of anirradiation source by using the irradiation source and thus stamping thefine concavo-convex patterns of the casting die only to the generatricesso as to form the surface patterns in form of an assembly of a pluralityof generatrices.

Particularly, a transparent substrate is fixed on a pressing plate and amaterial (a plastic layer colored by a colloidal carbon) which isthermoplastic and absorbs light beam is set on the opposed side of theplate and a no heat generation type casting die (made of a nickel alloy)is placed on the opposite to the plastic layer and a pressing force isgenerated in a dotted region between the casting die and the plasticlayer by using a stamp having projected faces only in the focal pointregion. Further, an irradiation source comprising laser, an opticalmodulator, and a lens system is set in the opposed side to the side ofthe casting die in relation to the plate.

When laser beam (radiant ray) is beamed to the plastic layer for formingan image at the focal point, the plastic layer absorbs the radiant rayand is heated at the focal point region. Simultaneously with the heatingby beaming radiant ray, pressure for stamping is applied by the stamp,so that point-like generatrix parts in the focal point region of theplastic layer are heated to the thermoplastic temperature and theseparts are deformed plastically corresponding to the fine structure ofthe casting die and even after cooling, the fine structure is fixed andthus predetermined fine concavo-convex patterns are formed.

Also, as a method for forming an optical diffraction structure providedwith the three-dimensional impression of a holographic image as well asthe brightness and clearness of a diffraction lattice, there is awell-known technique for obtaining one optical diffraction structure inwhich interference fringes for forming the diffraction lattices andholographic images coexist by carrying out exposure and development ofphotographic images and diffraction lattices on a dry plate through amask pattern (Japanese Patent Application Laid-Open No. 59-99475).

Further, production methods involving directly drawing lattice patternsof diffraction lattices and interference fringes of holographic imagessimulated using a computer by electron beam (Japanese Patent ApplicationLaid-Open Nos. 6-337315 and 11-24539) have been known in these years.

SUMMARY OF THE INVENTION

However, the conventional method described in the Japanese PatentApplication Laid-Open No. 61-20723 requires a stamp for applyingpressure and an apparatus such as a pressure generating apparatus. Thepressure generating apparatus comprises, for example, a ball holdingunit and a ball to be put in a cylindrical space and the space isconnected to a pressure generating source via a pneumatic pipe and asolenoid valve, and thus, the apparatus is complicated and thereforebecomes costly.

Further, in the case of generating pressure only in the focal pointregion by using a stamp, it is very difficult to apply pressureprecisely only to the predetermined fine region. Especially, in the casethe formation speed of the fine concavo-convex patterns is to beincreased, there is a limit to improve the formation speed only by themeans of mechanically applying pressure.

With respect to the method for producing the above-mentioned opticaldiffraction structure in which the interference fringes for formingholographic images and diffraction lattices coexist, the exposure workhas to be repeated and further development process is required and thusthe production process becomes complicated and troublesome and takes along time. Further, the above-mentioned production method by usingelectron beam requires a large scale apparatus and extremely complicatedcomputation, resulting in extremely high production cost and long timeand difficulty of the production of an optical diffraction structure ina scale as large as 100 cm² or larger.

Therefore, it is an object of the invention to provide a method forforming a fine concavo-convex pattern by which fine concavo-convexpatterns are formed by a simple apparatus and the formation speed of thefine concavo-convex patterns is increased.

Further, it is another object of the invention to provide a method forproducing and a method for copying an optical diffraction structurewhich neither cost high nor require troublesome work in the productionprocess.

To solve the above-mentioned problems, the invention provides a methodfor forming fine concavo-convex patterns summarized as follows:

(1) a method for forming fine concavo-convex patterns by using a reliefformation material having a relief formation layer composed of a resinhaving thermoplasticity and a relief pattern sheet having on a surfacethereof relief patterns corresponding to fine concavo-convex patterns ofa master hologram, wherein a photothermal conversion layer is formed inthe relief formation material or the relief pattern sheet; thephotothermal conversion layer is irradiated with light to make thephotothermal conversion layer generate heat in the state that the reliefformation material and the relief pattern sheet are brought into contactwith each other in such a manner that the relief formation layer isbrought into contact with the relief patterns; and the fineconcavo-convex patterns of the master hologram corresponding to therelief patterns are formed on the relief formation layer;

(2) the method for forming fine concavo-convex patterns according to theabove description (1), wherein the photothermal conversion layer isformed in the relief pattern sheet and the relief pattern sheet side isirradiated with the light;

(3) the method for forming fine concavo-convex patterns according to theabove description (1), wherein the photothermal conversion layer isformed in the relief formation material;

(4) the method for forming fine concavo-convex patterns according to theabove description (1) r wherein the relief formation layer is composedof an ionizing radiation-curable resin having thermoplasticity; and

(5) the method for forming fine concavo-convex patterns according to theabove description (1), wherein the relief formation material and therelief pattern sheet are closely attached to each other by vacuumadsorption.

Also, to solve the above-mentioned problems, the invention provides ahologram copying method as follows:

a hologram copying method for laminating a master hologram having anobject region to be copied having interference fringes to express ahologram image in a concavo-convex form on a fusion layer formed on abase substrate, and fusing the fusion layer by heat to transfer theinterference fringes to the fusion layer, wherein the master hologramand the fusion layer which are laminated mutually are irradiated with anenergy beam in such a manner that an irradiation range is limited to aportion of the object region to be copied to fuse the fusion layer inthe irradiation range by the heat based on the energy beam, and theinterference fringes are successively transferred to the fusion layer byshifting the irradiation range in such a manner of moving along theinterference fringes.

According to the invention, the mutually laminated fusion layer and themaster hologram is irradiated with energy beam and the irradiation rangeis heated by the heat of the energy beam to fuse the fusion layer. Sincethe irradiation range of the energy beam is limited to a portion of theregion to be copied in the master hologram, the range to be heated islimited to the irradiation range. Therefore, the range of the fusionlayer to be fused by the heat is limited to the irradiation range andonly the interference fringes included in the irradiation range of themaster hologram are transferred to the fusion layer. If the irradiationrange is shifted in such a manner os moving along the interferencefringes, with the shift, the fusion layer in the irradiation range issuccessively fused, and from the fused portions, the interferencefringes are transferred successively to the fusion layer.

In the invention, the concavo-convex forms of an existing masterhologram are successively transferred, so that no development process isrequired. Further, it is required only to move the energy beam beamed tothe laminated of the master hologram and the fusion layer, so that nocomplicated and large scale apparatus or system is necessary. Also,since the irradiation range of the energy beam to beam thereto is aportion of the region to be copied and the irradiation range is moved,the heat quantity kept in the fusion layer per a unit time can be keptlow. Accordingly, even if the portion which is in the irradiation rangeis once heated, the heat kept in the portion is soon releasedimmediately after the portion is out of the irradiation range, and thetemperature of the portion is decreased to a level at which the fusedfusion layer is hardened without any cooling facilities.

In the invention, “the region to be copied” means a range in the masterhologram where the interference fringes to be transferred in one timeprocess are formed. Accordingly, all of the interference fringes formedin the master hologram may be included in “the region to be copied” or aplurality of “the region to be copied” may be included in the masterhologram.

“Energy beam” means energy beams having heat themselves just likeso-called heat beam and also energy beams having no heat themselves.Accordingly, “heat of the energybeam” includes heat which the energybeam itself has and also heat which is generated by reaction occurringat the irradiation point of the energy beam, e.g. activation of electronor chemical reaction. An embodiment of irradiating the mutually layeredfusion layer and master hologram which are mutually laminated withenergy beam may include irradiation from the fusion layer side andirradiation from the master hologram side.

In the invention, a master hologram side may be irradiated with theenergy beam in form of light energy, and the fusion layer may contain asubstance for improving conversion efficiency from light energy to heatenergy. In this case, consideration of the transmission of the energybeam in the base substrate and respective layers laminated on the basesubstrate is not needed. Further, addition of the substance such ascarbon black for improving the conversion efficiency from light energyto heat energy to the fusion layer makes it easy to increase thetemperature in the irradiation range of the energy beam in the fusionlayer and the temperature in the portions out of the irradiation rangeis easy to get lower.

To solve the above-mentioned problems, the method for producing anoptical diffraction structure according to the invention comprises: acopying process including the steps of; laminating a master hologramhaving an object region to be copied having interference fringes toexpress a hologram image in a concavo-convex form on a fusion layerformed on a base substrate, irradiating the master hologram and thefusion layer which are laminated mutually with an energy beam in such amanner that an irradiation range is limited to a portion of the objectregion to be copied to fuse the fusion layer in the irradiation range byheat based on the energy beam, and transferring the interference fringessuccessively to the fusion layer by shifting the irradiation range insuch a manner of moving along the interference fringes; and a drawingprocess for drawing a predetermined shape on the fusion layer includingthe steps of; laminating a diffraction lattice on the fusion layer,irradiating the diffraction lattice and the fusion layer which arelaminated mutually with an energy beam in such a manner that anirradiation range is limited to a portion of the diffraction lattice tofuse the fusion layer in the irradiation range by heat based on theenergy beam, and transferring the diffraction lattice to the fusionlayer by shifting the irradiation range in such a manner of drawing thepredetermined shape.

Because of the same reasons as those in the case of the hologram copyingmethod, the copying process of the invention is carried out to copyholograms without any cooling facilities. Further, in the drawingprocess, since the irradiation range of the energy beam is limited to aportion of the diffraction lattice, the diffraction lattice only in arange corresponding to the irradiation range is transferred to thefusion layer by the same reasons as those in the case of the hologramcopying method. By shifting the irradiation range so as to draw apredetermined shape, the diffraction lattice as the predetermined shapecan be transferred to the fusion layer.

In a conventional hologram copying method by heating, since the entirebody of the master hologram is heated, the entire diffraction lattice iscopied by employing such a method. On the other hand, in the invention,since the irradiation range, that is the heating range, can be limitedto a portion of the diffraction lattice, a predetermined shape can bedrawn by the diffraction lattice because of the above-mentioned reasonsand the diffraction lattice in the predetermined shape and the copiedinterference fringes may be combined properly. In the invention,“optical diffraction structure” means a substance that at least aportion thereof has the optical diffraction structure of such as thediffraction lattice or a hologram.

In the method for producing an optical diffraction structure for theinvention, the interference fringes and the diffraction lattice may betransferred so as to form one image by combination of the hologram imageexpressed by the interference fringes transferred in the copying processand the predetermined shape transferred in the drawing process.Accordingly, the optical diffraction structure expressing one imagecomposed by combining the hologram image and the shape drawn by thediffraction lattices can be produced. The definition of the energy beamand the embodiment of the irradiation of the energy beam are same asdescribed above in the hologram copying method and descriptions of themare not repeated.

A master hologram side may be irradiated with the energy beam in form oflight energy, and the fusion layer may contain a substance for improvingconversion efficiency from light energy to heat energy. Because of thesame reasons as those in the above-mentioned hologram copying method,consideration of the transmission of the energy beam in the basesubstrate and respective layers layered on the base substrate is notneeded and the temperature rising property by heat based on the energybeam can be improved.

Further, the drawing process may comprise a first drawing process ofdrawing a first predetermined shape on the fusion layer by a firstdiffraction lattice produced by photographing interference fringes by aplurality of laser beams at a position of focused image formation of theinterference fringes by the plurality of laser beams; and a seconddrawing process of drawing a second predetermined shape on the fusionlayer by a second diffraction lattice produced by photographinginterference fringes of a plurality of laser beams at a position shiftedfrom the position focused image formation of the interference fringes bythe plurality of laser beams. Accordingly, in the produced opticaldiffraction structure, the interference fringes with the secondpredetermined shape focus on the point different in the depth directionfrom the interference fringes with the first predetermined shape.Consequently, pseudo-three-dimensional impression can be expressed inthe optical diffraction structure by the first and the secondpredetermined shapes.

To solve the above-mentioned problems, the method for copying an opticaldiffraction structure according to the invention includes the steps of:laminating an optical diffraction structure master-hologram having anobject region to be copied having optical interference fringes in aconcavo-convex form on a fusion layer formed on a base substrate,irradiating the optical diffraction structure master-hologram and thefusion layer which are laminated mutually with an energy beam in such amanner that an irradiation range is limited to a portion of the objectregion to be copied to fuse the fusion layer in the irradiation range byheat based on the energy beam, and transferring the interference fringessuccessively to the fusion layer by shifting the irradiation range inthe object region to be copied, wherein the step for transferringcomprises: a first transfer process of successively transferring theinterference fringes to the fusion layer by shifting the irradiationrange of the energy beam in a predetermined direction so as to drawscanning lines, and a second transfer process of successivelytransferring the interference fringes in a boundary part of each of thescanning lines drawn in the object region to be copied to the fusionlayer by irradiating the boundary parts with the energy beam andshifting the irradiation range of the energy beam in such a manner ofmoving along the scanning lines.

According to the invention, in the first transfer process, since theirradiation range of the energy beam is shifted in a predetermineddirection so as to draw a scanning, with the shifting, the temperaturein the portion of the fusion layer in the irradiation range is increasedby the heat based on the energy beam to fuse the portion of the fusionlayer and thus the interference fringes overlaid on the fused portionare successively transferred to the fusion layer. Next, in the secondtransfer process, the irradiation range is shifted along with thescanning lines while the energy beam is beamed to the boundary part ofeach scanning line drawn in the first transfer process. Accordingly, inthe second transfer process, the fusion layer in the boundary part ofthe scanning line in the first transfer process is fused by the heatbased on the energy beam, and with the shift of the energy beam, theinterference fringes in the boundary part of the scanning line aresuccessively transferred to the fusion layer along the scanning line.

In the invention, since both of the first transfer process and thesecond transfer process are only for successively transferring theconcavo-convex form of an existing optical diffraction structuremaster-hologram, no development process is required and also since onlyenergy beam is beamed to fuse the fusion layer, no complicated and largescale apparatus or system is required.

Further, since the energy quantity of the energy beam is high in thecenter part of the energy beam and low in the boundary part, the fusionlayer is easy to be fused in the center part of the irradiation range ofthe energy beam and relatively difficult to be fused in the boundarypart as compared with the center part. Therefore, in the surface of thefusion layer on completion of the first transfer process, the portion ofthe center part of the energy beam is mounted as compared with theportion of the boundary part and the surface of the fusion layer has adifference in the height. However, in the second transfer process, sincethe energy beam is beamed in such a manner that the boundary part of thescanning line of the energy beam in the first transfer process becomesthe center of the irradiation range, the portion which was difficult tobe fused by the energy beam in the first transfer process can be fused.Accordingly, the difference in the height of the surface of the fusionlayer caused by the first transfer process can be amended and as aresult, even in the case of carrying out copying by using the obtainedoptical diffraction structure as a master hologram, image deteriorationby the copying can be prevented.

In the invention, “optical diffraction structure” means a structureincluding a hologram for forming a hologram image and a diffractionlattice, having optical interference fringes in form of theconcavo-convex form, and generating a predetermined image based on thediffraction phenomenon of light. Further, “region to be copied” meansthe range in the optical diffraction structure master-hologram where theinterference fringes to be transferred in one time transfer process areformed. Accordingly, the “region to be copied” may include entireinterference fringes formed in the optical diffraction structuremaster-hologram and a plurality of “regions to be copied” may beincluded in the optical diffraction structure master-hologram. Theembodiment of “drawing a scanning line in one direction” includes thecase that respective lines are arranged in parallel if straight lines orwavy lines are employed as scanning lines transversely crossing theregion to be copied and the case that scanning lines are drawnconcentrically or spirally.

In the invention, “energy beam” means energy beams having heatthemselves just like so-called heat beam and also energy beams having noheat themselves. Accordingly, “heat of the energy beam” means heat whichthe energy beam itself has and also heat which is generated by reactionat the irradiation point of the energy beam, e.g. activation of electronor chemical reaction. An embodiment of energy beam irradiation to themutually laminated of the fusion layer and the master hologram mayinclude irradiation from the fusion layer side and irradiation from themaster hologram side. The relationship of the energy quantities of theenergy beam in comparison of the first transfer process and the secondtransfer process may be same in some cases and different in other casesand may properly be set so as to obtain the flatness of the fusion layerof the finally obtained optical diffraction structure, depending on thematerial of the fusion layer and the type of the energy beam.

In the invention, an energy dose of the energy beam in the secondtransfer process may be equal to or lower than that of an energy beam inthe first transfer process. The extent of the energy dose of the energybeam to be beamed is proportional to the size of the irradiation rangeand the size of the fused part of the fusion layer. Therefore, theenergy quantities may be made different as described above, so that thefused part in the first transfer process can be made large and the fusedpart in the second transfer process can be made same as or smaller thanthe fused part in the first process. In such a case, it is preferablethat the energy dose of the energy beam in the second transfer processis in a range of 0.3 to 1 time as much as that of the energy beam in thefirst transfer process. If it is in the range, with respect to thesurface of the fusion layer of the obtained optical diffractionstructure, it is made possible to obtain flatness sufficient to carryout copying without any undesirable consequences even if the obtainedoptical diffraction structure is used as a master hologram.

As the method for forming a fine concavo-convex pattern for theinvention employs a method for forming the fine concavo-convex patternsof the master hologram corresponding to relief patterns of a reliefpattern sheet in a relief formation layer by irradiating thephotothermal conversion layer with light to make the photothermalconversion layer generate heat in the state that the relief formationlayer of the relief formation material and the relief patterns of therelief pattern sheet are brought into contact with each other, so thatas compared with a conventional method involving heating by beamingradiant ray and simultaneously applying pressure for stamping with astamp, this method for the invention requires for the relief formationlayer and the relief patterns only to contact with each other but nopressure application. Therefore, it is no need to use any apparatus suchas the stamp or a pressure generating apparatus composed of complicatedunits and the apparatus can be simplified and the cost of the apparatuscan be low.

Unlike the conventional method, it is no need to apply pressure only inthe focal point region and to apply pressure precisely to only apredetermined narrow region. It is sufficient for the relief formationlayer and the relief patterns to be brought into contact with each otherevenly as a whole and the both can be brought into contact with eachother extremely easily, so that the fine concavo-convex patterns caneasily and reliably be formed. Further, since it is sufficient for therelief formation layer and the relief patterns to be brought intocontact with each other and different from the conventional method, itis no need to apply pressure partially to a small region, the formationspeed of the fine concavo-convex patterns can easily be increased.

In the invention, since the relief formation layer and the reliefpatterns are brought into contact with each other without pressure andno pressure is applied to the relief formation layer and the reliefpatterns, no damage owing to pressure is caused in them. Even materialsweak to heat or pressure may be usable for the relief formation materialor the substrate of the relief pattern sheet.

Also in the invention, in the case the photothermal conversion layer isformed in the relief pattern sheet side, it is no need to form anyphotothermal conversion layer to be colored dark by carbon black or thelike in the relief formation material side and thus dark coloration ofthe relief formation material side can be avoided. Therefore, a producthaving fine concavo-convex patterns can be colored with any optionalcolor and the invention can be applied to produce a variety of products.

Further, in the case of heating the photothermal conversion layer bybeaming light, the light irradiation is carried out patternwise, so thatthe photothermal conversion layer can be made generate heat patternwiseand the relief patterns can be heated in optional patterns andaccordingly, simultaneously with the formation of the fineconcavo-convex patterns, on-demand information can be produced.

If the relief formation material and the relief pattern sheet areclosely attached to each other by vacuum adsorption, the reliefformation layer of the relief formation material and the relief patternsof the relief pattern sheet are reliably brought into contact with eachother and therefore, the fine concavo-convex patterns can be formed morereliably.

According to the hologram copying method and the method for producing anoptical diffraction structure for the invention, the diffraction latticeand the hologram can be expressed as one image only by beaming energybeam to a portion of the region to be copied in the master hologram andthe diffraction lattice without costing high or taking troublesome work.

Further, according to the copying method for the optical diffractionstructure of the invention, stable optical diffraction structure can becopied without costing high or taking troublesome work by beaming energybeam to the optical diffraction structure master-hologram while drawingscanning lines in one direction and then beaming energy beam in theboundary parts of each of the scanning lines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C show one example of the diagrams of a method for formingfine concavo-convex patterns according to the invention;

FIGS. 2A to 2C show another example of the diagrams of a method forforming fine concavo-convex patterns according to the invention;

FIG. 3 shows an explanatory drawing schematically showing one example ofan apparatus to be employed for the method for forming fineconcavo-convex patterns according to the invention;

FIGS. 4A to 4F show the diagrams of the relief pattern formation methodfrom a master hologram by 2 P method;

FIG. 5 shows the state that the bright point is moving depending on thediffraction lattice area;

FIG. 6 shows one example of the first image body formed by the apparatusshown in FIG. 3;

FIG. 7 shows the state that the image body shown in FIG. 6 is formed bythe apparatus shown in FIG. 3;

FIG. 8 shows one example of the second image body formed by theapparatus shown in FIG. 3;

FIG. 9 shows a plurality of generatric regions contained in one dividedregion;

FIG. 10 shows the state that the image body shown in FIG. 8 is formed bythe apparatus shown in FIG. 3;

FIG. 11 shows the third image body formed by the apparatus shown in FIG.3;

FIG. 12 is a magnified diagram of the third image body shown in FIG. 11;

FIG. 13 shows the state that the background region is formed by theapparatus shown in FIG. 3;

FIG. 14 shows the state that fine regions are formed by the apparatusshown in FIG. 3;

FIG. 15 shows an optical diffraction structure production apparatus tobe used an embodiment for executing a method for producing an opticaldiffraction structure and a method for copying an optical diffractionstructure for the invention;

FIG. 16 shows the state that a master hologram to be used in theembodiment of FIG. 15 and a film for forming hologram are laminated;

FIG. 17 shows the state that the master hologram and the film forforming hologram shown in FIG. 16 are irradiated with IR laser;

FIG. 18A shows one example of a master hologram to be used in anembodiment shown in FIG. 15, and FIG. 18B shows the state that themaster hologram shown in FIG. 18A is irradiated with IR laser;

FIG. 19A shows the state that a predetermined shape is drawn by IRlaser, and FIG. 19B shows one example of an optical diffractionstructure produced in the embodiment of FIG. 15;

FIG. 20 shows one example of a master hologram to be used in theembodiment shown in FIG. 15;

FIG. 21A shows the state that the master hologram is scanned by IR laserin the first transfer process, and FIG. 21B is a cross-sectional view ofa fusion layer obtained by the first transfer process; and

FIG. 22A shows the state that the master hologram is scanned by IR laserin the second transfer process, and FIG. 22B is a cross-sectional viewof a fusion layer obtained by the second transfer process.

DETAILED DESCRIPTION OF THE INVENTION

First of all, an embodiment of execution of a method for forming a fineconcavo-convex pattern for the invention will be described. Firstly, asshown in FIG. 1A, a relief formation material 3 provided with a reliefformation layer 2 of a thermoplastic ionizing radiation-curable resinfor forming fine concavo-convex patterns is formed on the surface of asubstrate 1 composed of a polyethylene terephthalate film and so on, anda relief pattern sheet 6 having relief patterns 5 corresponding to thefine concavo-convex patterns of the master hologram is laminated on asubstrate 4 composed of a polyethylene terephthalate film and so on. Aphotothermal conversion layer 7 is formed between the substrate 1 of therelief formation material 3 and the relief formation layer 2.

Next, as shown in FIG. 1B, in the state that the relief formationmaterial 3 and the relief pattern sheet 6 are brought into contact witheach other in such a manner that the relief formation layer 2 and therelief patterns 5 are closely attached, the photothermal conversionlayer 7 is irradiated with light 8 such as laser beam from the substrate4 side of the relief pattern sheet 6. The photothermal conversion layer7 generates heat in the portion where the light is beamed. The heat ofthe photothermal conversion layer 7 is transmitted to the portion of therelief formation layer 2 contacting the heated portion of thephotothermal conversion layer 7 to heat and fuse the thermoplastic resinof the relief formation layer 2. In the fused or softened reliefformation layer 2, since the relief patterns 5 are closely attached tothe relief formation layer 2, the fine concavo-convex shape,corresponding to the relief patterns 5 is formed in the relief formationlayer 2.

In this method for the invention, the relief patterns 5 are brought intocontact with and closely attached to the relief formation layer 2 and itis no need to apply pressure between the relief formation material 3 andthe relief pattern sheet 6. However, to keep the close adhesion state ofthe relief formation layer 2 and the relief patterns 5, a laminateobtained by laminating the relief formation material 3 and the reliefpattern sheet 6 may be sandwiched between supporting bodies of glassplates or the like to fix and hold the laminate.

If air exists between the relief patterns 5 and the relief formationlayer 2, since the air possibly works as a heat insulating layer and itis therefore possible that heat is not well transmitted from the reliefpatterns 5 to the relief formation layer 2, air entrainment shouldcarefully be avoided. To closely attach the relief formation layer 2 andthe relief patterns 5 to each other without any air entrainment betweenthem, the adhesion of the relief formation layer 2 and the reliefpatterns 5 may be carried out by vacuum adsorption for sucking andevacuating air between them by a vacuum pump or the like.

On completion of the light irradiation, when the relief pattern sheet 6is separated from the relief formation material 3 in the state that therelief formation layer 2 composed of the thermoplastic resin is cooled,as shown in FIG. 1C, the fine concavo-convex patterns 9 of the masterhologram are formed on the surface of the relief formation layer 2 and arelief pattern formation body 10 having the fine concavo-convex patterns9 fixed thereon is obtained. After that, ionizing radiation is beamed tothe relief formation layer 2 having the fine concavo-convex patterns 9thereon to cure the ionizing radiation-curable resin of the reliefformation layer 2.

FIGS. 2A to 2C show another example of the flow diagrams of a method forforming a fine concavo-convex pattern according to the invention. In theembodiment of the invention shown in FIGS. 1A to 1C, the photothermalconversion layer 7 is formed in the relief formation material 3 side andlight irradiation is carried out from the relief pattern sheet 6 side,however the photothermal conversion layer 7 may be formed in the reliefpattern sheet 6 side. More particularly, as shown in FIG. 2A, thephotothermal conversion layer 7 is formed between the substrate 4 of therelief pattern sheet 6 and the relief patterns 5 and the reliefformation material 3 is composed of the substrate 1 and the reliefformation layer 2 without photothermal conversion layer.

As shown in FIG. 2B, the relief pattern sheet 6 and the relief formationmaterial 3 are closely attached to each other so as to bring the reliefformation layer 2 and the relief patterns 5 into contact with eachother. Then, as shown in the same figure, the photothermal conversionlayer 7 is irradiated from the relief pattern sheet 6 side with light 8to generate heat at the photothermal conversion layer 7 and thus thethermoplastic resin of the relief formation layer 2 is fused or softenedto form the fine concavo-convex shape corresponding to the reliefpatterns 5 in the relief formation layer 2.

On completion of light irradiation, in the state that the reliefformation layer 2 composed of the thermoplastic resin is cooled, whenthe relief pattern sheet 6 is separated from the relief formationmaterial 3, as shown in FIG. 2, the fine concavo-convex patterns 9 ofthe master hologram are formed on the surface of the relief formationlayer 2 to obtain the relief pattern formed body 10 in which the fineconcavo-convex patterns 9 are fixed, and similarly to the embodimentshown in FIGS. 1A to 1C, ionizing radiation is beamed to the reliefformation layer 2 having the fine concavo-convex patterns 9 formedthereon to cure the ionizing radiation-curable resin of the reliefformation layer 2.

In this case, as shown in FIG. 2, since the finally obtained reliefpattern formed body 10 has no photothermal conversion layer 7, therelief pattern formed body may be colored with any optional color and itcan cause excellent design.

To beam light 8 to the photothermal conversion layer 7, for example anapparatus for generating laser beam may be employed. Further, in thecase of beaming light to the photothermal conversion layer 7, light isbeamed at spots from an irradiation source while the spots to which thelight is beamed being moved so as to scan a predetermined region andthus the light irradiation is carried out to a desired portion. Bybeaming light in such a manner, heat generation in the necessary andoptimum quantity can be carried out only for needed parts of thephotothermal conversion layer 7 and therefore, the effect of heat can besuppressed to the minimum. Further, in the case of beaming light to thelaminate body of the relief pattern sheet 6 and the relief formationmaterial 3, as a support for the laminate body, an XY stage, a drum orthe like can be used.

FIG. 3 shows an explanatory drawing schematically showing one example ofan apparatus to be employed for the method for forming a fineconcavo-convex pattern according to the invention. The apparatus shownin FIG. 3 comprises a laser head 21 as a light irradiation source and anXY stage 22 for controlling the irradiation position. The laser head 21is provided with a laser driver 25 as a control system capable ofadjusting or turning on or off output energy of the light source and isconstructed to be controlled by a PC 24. Further, the laser head 21 isalso provided with an optical system such as mirrors and lens foradjusting the laser light source, and the optical path and the focalpoint of the emitted light. The XY stage 22 is formed so as to set alaminate body 23, which is obtained by closely attaching the reliefformation material 3 and the relief pattern sheet 6 to each other, onthe surface and an XY stage controller 26 for controlling the movementof the XY stage 22 is connected so as to control the movement by the PC24.

To carry out light irradiation by scanning light in spot form by usingthe apparatus shown in FIG. 3, the laminate body 23, which is obtainedby closely attaching the relief formed body 3 and the relief patternsheet 6 to each other, is set on a predetermined position of the surfaceof the XY stage 22. When the irradiation pattern is instructed from thePC 24, the laser head 21 is positioned as a starting point and the XYstage 22 is moved and the laser beam irradiation by the laser head 21 isturned on or off to carry out light irradiation in the predeterminedpattern.

The light 8 beamed from the laser head 21 is made to be in spot shapewith a diameter of not over 100 μm and is used for scanning the laminatebody 23 along with a predetermined scanning pattern in the XY directionby operation of the XY stage 22 so as to irradiate the entire body ofthe laminate body 23 with the light 8. The photothermal conversion layer7 of the laminate body 23 is irradiated with the laser beam as a smallspot and the spot of the laser beam is successively moved by thescanning, so that the duration of the laser beam irradiation isextremely short. As a result, only a very narrow region like the spot inthe relief formation layer 2 or the relief patterns 5 contacting thephotothermal conversion layer 7 is heated for a short time, and afterwhen the resin of the relief formation layer 2 is fused to form thepattern, the resin is cooled soon and the pattern formation state isimmediately fixed.

At the time of irradiating the photothermal conversion layer 7 withlight 8, it is preferable to properly select the wavelength of the lightwith a high transmittance to the substrate 1 and the substrate 4 so asto cause no damage on these substrates with the light transmittedthrough the substrates. For example, in the case of using laser beam anda polyethylene terephthalate film (sometimes referred to as PET) for thesubstrates 1 and 4, laser beam near the visible light and havingwavelength with high transmittance to PET may properly be selected.

In the case of irradiating the photothermal conversion layer 7 withlight, on-demand information can be produced by beaming lightpatternwise, not entirely, along with an any optional pattern, andgenerating heat in the photothermal conversion layer 7 patternwise toheat the relief formation layer 2 or the relief patterns 5 in theoptional shape. As on-demand information, for example, particularinformation such as ID numbers of individuals can be used.

The concavo-convex patterns in which general information or commoninformation such as a company's name is recorded are formed in theentire body of the relief formation layer 2 and on the portions of thegaps other than the regions where the concavo-convex patterns are formedor on the above-mentioned concavo-convex patterns, letters and signs ofthe particular information are directly drawn and recorded in form ofconcavo-convex patterns by scanning with the laser beam. In such amanner, the concavo-convex patterns of the common information are formedand at the same time, on-demand information can be recorded. Theconcavo-convex pattern formed body in which the particular informationis recorded in the above-mentioned manner can improve the security if itis used as a security card such as an ID card.

The material placed between the photothermal conversion layer 7 and thelight source (e.g. in the case of beaming light from the substrate 4side in FIGS. 1A to 1C and FIGS. 2A to 2C, the substrate 4 and therelief patterns 5 shown in FIGS. 1A to 1C and the substrate 4 shown inFIGS. 2A to 2C) may be any material which can practically transmit lightso as to lead light to the photothermal conversion layer 7.

As the ionizing radiation for curing the relief formation layer 2 of theionizing radiation-curable resin in which the fine concavo-convexpatterns 9 are formed, all kinds of UV rays (UV-A, UV-B, and UV-C),visible light rays, γ-beam, x-rays, and electron beam may be employedand UV rays and electron beam are preferable. With respect to theionizing radiation apparatus 50, in the case UV rays as the ionizingradiation are beamed, as the light source, a UV lamp such as an ultrahigh pressure mercury lamp, a high-pressure mercury lamp, a low pressuremercury lamp, a carbon arc, a black light, a metal halide lamp or thelike is used. The wavelength of the UV rays is generally about 200 to400 nm and the wavelength may be selected depending on the compositionof the resin layer. The irradiation dose is also controlled depending onthe composition of the resin layer, the output power of the UV lamp, andthe processing speed.

In the case electron beam is beamed as the ionizing radiation, theapparatuses to be employed are those which comprise various kinds ofelectron beam accelerators such as Cockcroft-Walton type, Van de Graafftype, the resonance transformer type, the insulator core transformertype, the linear type, the dynamitron type, and the high frequency typeand which can beam electron beam in electron curtain manner or beamscanning manner or the like. Preferably, “Electro-curtain” (trade name)which can beam electron beam evenly in the curtain manner from a linearfilament can be exemplified. The irradiation dose of the electron beamis controlled by beaming about 0.5 to 20 Mrad of electron beam withelectrons having energy of generally 100 to 1,000 keV, preferably 100 to300 keV. With respect to the atmosphere at the time of irradiation, theoxygen concentration is controlled to be not over 500 ppm, preferablyabout 200 ppm in general.

Hereinafter, the relief formation material 3 and the relief patternsheet 6 will be described more in details.

As the substrate 1 of the relief formation material 3, any film type(including sheet type) material may be used without any particularlimitation. Practical examples of usable films are polymer films(plastic films) such as films of polyester resins, e.g. polyethyleneterephthalate, polybutylene terephthalate, polyethylene naphthalate,polyethylene terephthalate-isophthalate copolymer, terephthalicacid-cyclohexanedimethanol-ethylene glycol copolymer, and extruded filmof polyethylene terephthalate/polyethylene naphthalate mixture;polyamide type resins, e.g. nylon 6, nylon 6,6, and nylon 610;polyolefin type resins, e.g. polyethylene, polypropylene, andpolymethylpentene; vinyl type resins, e.g. poly vinyl chloride; acrylictype resins, e.g. polyacrylate, polymethacrylate, andpolymethylmethacrylate; imide type resins; engineering plastics, e.g.polyarylate, polysulfone, polyether sulfone, polyphenylene ether,polyphenylene sulfide (PPS), polyaramide, polyether ketone, polyethernitrile, polyether ether ketone, and polyether sulfide; styrene typeresin, e.g. polycarbonate and ABS resin; and cellulose type films, e.g.cellophane, cellulose triacetate, cellulose diacetate, andnitrocellulose. The above-mentioned plastic films may be stretched filmsor non-stretched films and in terms of the strength improvement,uniaxially or diaxially stretched films are preferable.

As the substrate 1, other than the plastic films, paper, syntheticpaper, and metal films such as iron and aluminum can be used. In termsof the light transmission property, plastic films are preferable. Theabove-mentioned films may be used alone or laminates of two or morekinds of the above-mentioned films may be used. The thickness of thesubstrate 1 is generally about 5 to 2000 μm. In general, as thesubstrate 1, a film of a polyester such as polyethylene terephthalate orpolyethylene naphthalate is used preferably since it has heatresistance, size stability, and ionizing radiation resistance and a filmof polyethylene terephthalate is used more preferably.

Prior to the application of a composition of the relief formation layer2, the face of substrate 1 to be coated may be subjected to treatmentfor easy adhesion such as corona discharge treatment, plasma treatment,ozone treatment, flame treatment, primer (sometimes called as anchorcoating, adhesion promoter, or easy adhesive) treatment, preheatingtreatment, dust removal treatment, or alkaline treatment. Also, based onthe necessity, the substrate 1 may contain additives such as a filler, aplasticizer, a coloring agent, or an antistatic agent.

As the resin having thermoplasticity to be used for the relief formationlayer 2, ionizing radiation-curable resins in solid state at a normaltemperature and having heat formability are preferably used. Suchionizing radiation-curable resins contain thermoplastic substanceshaving radical polymerizable unsaturated groups. Practically there arefollowing two types of resins.

(1) Polymers having a glass transition temperature of 0 to 250° C. andcomprising radical polymerizable unsaturated groups; more particularly,polymers or copolymers of the following compounds i) to viii) into whichthe radical polymerizable groups are introduced by the following methods(a) to (d);

i) monomers having hydroxyl: N-methylolacrylamide, 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutylmethacrylate, 2-hydroxy-3-phenoxypropyl methacrylate,2-hydroxy-3-phenoxypropyl acrylate, and the like;

ii) monomers having carboxyl: acrylic acid, methacrylic acid,acryloyloxyethyl monosuccinate, and the like;

iii) monomers having epoxy groups: glycidyl methacrylate and the like;

iv) monomers having aziridinyl: 2-aziridinylethyl methacrylate, allyl2-aziridinyl propionate, and the like;

v) monomers having amino groups: acrylamide, methacrylamide,diacetoneacrylamide, dimethylaminoethyl methacrylate, diethylaminoethylmethacrylate, and the like;

vi) monomers having sulfonyl: 2-acrylamido-2-methylpropanesulfonic acid,and the like;

vii) monomers having isocyanate groups: radical polymerizable monomerhaving adduct of diisocyanate such as an equimolecular adduct of2,4-toluene diisocyanate and 2-hydroxyethyl acrylate and activehydrogen; and,

viii) In order to adjust the glass transition point of theabove-mentioned polymers or copolymers or to adjust the physicalproperties of the cured films, the above-mentioned monomers can becopolymerized with the following copolymerizable monomers: methylmethacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate,propyl acrylate, propyl methacrylate, butyl acrylate, butylmethacrylate, isobutyl acrylate, isobutyl methacrylate, t-butylacrylate, t-butyl methacrylate, isoamyl acrylater isoamyl methacrylate,cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate,2-ethylhexyl methacrylate, and the like.

The methods (a) to (d) for introducing radical polymerizable unsaturatedgroups into the above-mentioned polymers are as follows.

(a) In the case of polymers or copolymers of monomers having hydroxyl,condensation reaction of monomers having carboxyl such as acrylic acidand methacrylic acid is carried out;

(b) in the case of polymers or copolymers of monomers having carboxyl orsulfone groups, condensation reaction of the above-mentioned monomershaving hydroxyl is carried out;

(c) in the case of polymers or copolymers of monomers having epoxygroups, isocyanate groups, oraziridinyl, addition reaction of theabove-mentioned monomers having hydroxyl or carboxyl is carried out; and

(d) in the case of polymers or copolymers of monomers having hydroxyl orcarboxyl, addition reaction of monomers having epoxy groups, monomershaving aziridinyl, or adducts of diisocyanate compounds andhydroxyl-containing acrylic acid esters in 1:1 mole ratio.

To carry out the above-mentioned reaction, it is preferable to add aslight amount of a polymerization inhibitor such as hydroquinone and tosend dry air.

(2) Compounds having a fusing point of 0 to 250° C. and comprisingradical polymerizable unsaturated groups; more particularly, stearylacrylate, stearyl methacrylate, triacryl isocyanurate, cyclohexanedioldiadrylate, cyclohexanediol dimethacrylate, spiroglycol diacrylate,spiroglycol dimethacrylate, and the like.

As the resin of the relief formation layer 2, mixtures of theabove-described (1) and (2) may be used and also mixtures furthercontaining the radical polymerizable unsaturated monomers may be used.The radical polymerizable unsaturated monomers are for improving thecrosslinking density and heat resistance at the time of ionizingradiation and examples to be used as the monomers other than the aboveexemplified compounds are ethylene glycol diacrylate, ethylene glycoldimethacrylate, polyethylene glycol diacrylate, polyethylene glycoldimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,trimethylolpropane diacrylate, trimethylolpropane dimethacrylate,pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate,pentaerythritol triacrylate, pentaerythritol trimethacrylate,dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate,ethylene glycol diglycidyl ether diacrylate, ethylene glycol diglycidylether dimethacrylate, polyethylene glycol diglycidyl ether diacrylate,polyethylene glycol diglycidyl ether dimethacrylate, propylene glycoldiglycidyl ether diacrylate, propylene glycol diglycidyl etherdimethacrylate, polypropylene glycol diglycidyl ether diacrylate,polypropylene glycol diglycidyl ether dimethacrylate, sorbitoltetraglycidyl ether tetraacrylate, sorbitol tetraglycidyl ethertetramethacrylate, and the like. It is preferably to use them in anamount of 0.1 to 100 parts by weight in 100 parts by weight of the solidmatter of the above-mentioned copolymer mixtures.

The above-mentioned ionizing radiation-curable resin is sufficientlycured by electron beam and in the case curing is carried out by UVirradiation, it is better to add a photopolymerization initiator such asacetophenones, benzophenones, Michlers's benzoyl benzoate, α-aminoximeester, tetramethylmeuram monosulfide, and thioxanthones and base on thenecessity, a photosensitizer such as n-butylamine, triethylamine, andtri-n-butylphosphine.

The above-mentioned ionizing radiation-curable resin can be cured byheat energy if a proper catalyst exists.

The ionizing radiation-curable resin being in solid state at a normaltemperature and having heat formability to be used for the reliefformation layer 2 is applied to the substrate 1 in a thickness ofgenerally 0.1 to 50 μm, preferably 0.5 to 5 μm, in the case a hologramis copied in form of concavo-convex patterns. The thickness differsdepending on intended use of the fine concavo-convex patterns to becopied.

The relief formation layer 2 can be formed on the substrate 1 by knowncoating method such as spin coating, knife coating, roll coating, or barcoating. In the case of forming the relief formation layer 2 on aportion of the substrate 1, a common printing technique such as screenprinting and gravure printing, or a transfer method can be employed.

With respect to the relief formation material 3 comprising the reliefformation layer 2 of the ionizing radiation-curable resin in solid stateat a normal temperature formed on the substrate 1, since the reliefformation layer 2 is formed in solid state at a normal temperature toform in a finger-touch-dry state, the material 3 can be stored whilebeing laminated.

A separation layer (not illustrated) may be formed between the substrate1 and the relief formation layer 2. The separation layer can provideseparation property, wear resistance, and printing suitability betweenthe substrate 1 and the relief formation layer 2. As the resin of theseparation layer, a wide range of conventionally known resins such asacrylic resins, cellulose type resins, vinyl resins, polyester resins,urethane resins, olefine resins, amide resins, and epoxy resin may beused. The thickness of the separation layer is generally 0.05 to 10 μm,preferably 0.2 to 2 μm.

The relief patterns 5 of the relief pattern sheet 6 are formed asconcavo-convex patterns corresponding to the fine concavo-convexpatterns 9 of the master hologram. As the fine concavo-convex patterns9, holograms such as relief holograms, optical diffraction structuresuch as diffraction lattice, and hair lines may be used.

As the images of the hologram, photographed images of actual objects,signs, letters, numerals, and illustrations may be used. The hologramimages themselves can be obtained by calculation of hologram diffractionlattices, or can be produced with a proper means such as a holographicstereogram from digital images taken by a digital camera of from two- orthree-dimensional images data of digital images of computer graphicsother than photography of an actual object. The diffraction lattices canexpress images of letters or the like by their outlines.

For the relief hologram, a hologram where light intensity distributionsof interference fringes caused by light interference between objectlight is recorded in form of ragged patterns and reference light anddiffraction lattices can be employed. As the relief hologram, there arelaser regeneration hologram such as Frenel hologram, Fraunhoferhologram, lens-less Fourier transform hologram, and image hologram;incandescence regeneration hologram such as rainbow hologram; and alsoholograms based on their principles: color hologram; computer hologram;hologram display; multiplex hologram; holographic stereogram; andholographic diffraction lattice.

As the diffraction lattice, there are holographic diffraction latticeusing hologram recording means; and further any optional diffractionlattice based on calculation by mechanically or graphically producingdiffraction lattice with a precision lathe or an electron beam drawingapparatus.

These hologram and diffraction lattice may be recorded singly ormultiple-recorded or recorded in combination. The diffraction latticecan give particular brightness with excellent design properties byassembling a plurality of regions different in the ridge directionand/or ridge interval and/or shape of the concavo-convex form and/orheight of the concavo-convex form, that is, regularly or randomlycombining a plurality of regions having different diffractiondirections.

A variety of known methods may be employed as a method for formingrelief patterns 5 on the surface of the substrate 4 from the fineconcavo-convex patterns of a master hologram. As a method for formingthe relief patterns 5, there are methods: (1) a hologram copying method(called as semi-dry copying method) described in Japanese PatentApplication Laid-Open No. 6-85103 by forming fine concavo-convexpatterns of a master hologram for copying on an ionizingradiation-curing resin by pressure application, beaming ionizingradiation after or simultaneously with the pressure application, andseparating the resin and the master hologram and (2) a photopolymerization method (called as 2 P method) by applying an ionizingradiation-curable resin in liquid state to the surface of the masterhologram for copying, curing the resin by beaming ionizing radiationafter spreading the resin on the surface to form fine ragged patterns,and obtaining a stamper by separating the formed resin from the masterhologram for copying.

Hereinafter, the above-mentioned 2 P method will be described. FIG. 4Ato FIG. 4F show the flow diagrams of the relief pattern formation methodfrom a master hologram by 2 P method. As shown in FIG. 4A, a masterhologram 11 having an uneven relief is used and as shown in FIG. 4B, anionizing radiation-curable resin composition 12 is dropwise titrated onthe master hologram 11. Next, as shown in FIGS. 4C and 4D, the substrate14 is set on the resin and pressurized to spread the ionizingradiation-curable resin composition 12 to evenly fill the recessedparts. Next, as shown in FIG. 4E, ionizing radiation such as UV rays isbeamed from the master hologram 11 side or the substrate 14 side to curethe ionizing radiation-curable resin composition 12. As shown in FIG.4F, the ionizing radiation-curable resin composition 13 and thesubstrate 14 united together by curing are separated form the masterhologram 11 to obtain a relief pattern sheet 6 comprising the ionizingradiation-curable resin composition 13 on the substrate 14 (thesubstrate 4) having the relief patterns 5.

As the material of the substrate 4 of the relief pattern sheet 6,metals, glass, or plastic films may be used. For example, in the casefine concavo-convex patterns are formed by rolling the relief patternsheet 6 and the relief formation material 3 on the surface of a rollformed as a cylindrical cylinder, since it is easy to practicallytransmit the light beamed from a light irradiation apparatus, a plasticfilm is used preferably. As the plastic film to be used as the substrate4, for example, a plastic film exemplified for the substrate 1 of therelief formation material 3 may be used.

The photothermal conversion layer 7 may be formed on the reliefformation material 3 side, the relief pattern sheet 6 side, or bothsized. The photothermal conversion layer 7 is any if it can absorb light8 and convert the light to heat to generate heat and may be a layerformed using a binder resin such as thermoplastic resin and aheat-curable resin in which a light absorbing coloring material such ascarbon black is dissolved or dispersed. The thickness of thephotothermal conversion layer 7 is generally 0.1 to 5 μm and preferably0.3 to 3 μm.

Other than carbon black, as the light absorbing coloring material to beused for the photothermal conversion layer 7, a variety of compounds canbe used depending on the light to be beamed. For example, as a coloringmaterial suitable for semiconductor laser, there are coloring materialssuch as polymethine type such as cyanine type and pyrylium type;phthalocyanine type coloring materials such as copper phthalocyanine;naphthalocyanine type coloring materials; dithiol metal complex typecoloring materials; naphthoquinone type coloring materials;anthraquinone type coloring materials; tirphenylmethane type coloringmaterials; aluminum type coloring materials; and diimmonium typecoloring materials. The photothermal conversion layer 7 can be formed byknown coating means.

As the binder resin to be used for the photothermal conversion layer 7,polyesters; acrylic, epoxy, butyral and acetal resins; vinylchloride-vinyl acetate copolymer; polyurethanes; thermoplastic highmolecular weight epoxy can be exemplified. Polyesters are preferable.

The relief pattern formed body 10 obtained by a method for forming afine concavo-convex pattern for the invention may be used as a masterhologram for copying as it is. It may be used in a label form bylayering an adhesive or separation paper on the substrate 1 side or atransfer material for hot stamp or a material for heat transfer using athermal head by making it as a transfer foil by forming an adhesivelayer in the substrate side.

Next, an image formation method for obtaining particular brightness withexcellent design properties by combining a plurality kinds of reliefpatterns 5 by employing a method for forming the relief patterns 5 onthe above-mentioned relief formation material 3 will be described. Thephotothermal conversion layer 7 can be provided either in the reliefpattern sheet 6 or in the relief formation material 3 to be used in theformation method described below.

A plurality of relief pattern sheets 6 having diffraction latticepatters as relief patterns 5 are made ready in such a manner that theorientation angles of the diffraction lattice patterns are madedifferent from one another and the respective diffraction latticepatterns are formed on relief formation layers 2 in such a manner thatthe transferred diffraction lattice patterns are adjoined with eachother in a predetermined direction on the relief formation material 3.

Accordingly, if the diffraction lattice patterns are rotated, imagepatterns composed of bright points of the diffraction light rays areobserved as if they are moving and so-called moving images are formed.The moving state may include continuous, semi-continuous, ordiscontinuous in a predetermined direction. To produce a state that thebright points are made as if they are moving continuously in a commonenvironments, the alteration of the orientation angles of the adjoiningdiffraction lattices within 5 degrees. If the angles are changed morethan that, the bright points move semi-continuously or discontinuously.“Orientation angles” means the angles of plane directions of the linescomposing the diffraction lattices.

The bright points of the respective diffraction lattice areas K1 . . .Kn are determined by the orientation angles and the diffraction anglesof diffraction lattices. For example, the case that a diffractionlattice area K1 has an orientation angle φ1 and a diffraction angle ψ1and a adjoining diffraction lattice area K2 has an orientation angle φ2and a diffraction angle ψ2 when light comes in at a predetermined anglewill be described. As shown in FIG. 5, when a first image I-1 is rotatedon an XY plane, the bright point in relation to a hemisphere HS isshifted to a bright point L2 of the diffraction lattice area K2 from abright point L1 of the diffraction lattice area K1. Accordingly, aplurality kinds of diffraction lattice patterns 5 having the respectivediffraction lattice areas K1 . . . Kn whose bright points haveorientation angles and diffraction angles so as to draw a desired shapeon the hemisphere HS may be selected. The diffraction angles aredetermined based on the diffraction lattice pitches and alteration ofthe bright points can be obtained in the perpendicular direction bychanging the diffraction angles.

Hereinafter, while exemplifying the first image I-1 shown in FIG. 6 asan image body giving a moving image, its formation method will bedescribed. In the formation method, relief pattern sheets 6 havingdiffraction lattice patterns as the relief patterns 5 are used.Hereinafter, the relief patterns 5 are called as the diffraction latticepatterns 5 in the formation method. The first image body I-1 is composedas a diffraction lattice row R of a plurality of diffraction latticeareas K1 . . . Kn with different orientation angles, which adjoin eachother in the predetermined direction H.

Next, based on the diffraction lattice patterns selected in theabove-mentioned manner, a method for forming the diffraction lattice rowR will be described practically along with FIG. 7. First, a reliefpattern sheet 6 having the diffraction lattice pattern 5 correspondingto the diffraction lattice area K1 and a relief formation material 3 areclosely attached to obtain a laminate 23 in the above-mentioned mannerand the laminate 23 is disposed on a predetermined position of an XYstage 22. Successively, the photothermal conversion layer 7 isirradiated with light 8 so as to form the diffraction lattice pattern 5on the region A of the relief formation layer 2 where the diffractionlattice area K1 is to be formed.

When light 8 is moved in the area A so as to draw scan lines SC1 atpredetermined pitches, the diffraction lattice pattern 5 is formed onlyin the area A and as a result, the diffraction lattice area K1 is formedin the area A where the area K1 is to be formed. The scanning lines SC1are made visible for making the explanation easily understandable, andtherefore, they are not actually observed with the naked eye. Theirradiation starting position and the irradiation pattern of the light 8may be controlled by control with PC 24. With respect to otherdiffraction lattice areas K2 . . . Kn respectively, in the same manneras that in the case of the diffraction lattice area K1, thecorresponding diffraction lattice patterns 5 may be formed in regionswhere the diffraction lattice patterns 5 are to be formed so as to makethe areas K2 . . . Kn adjoining in the predetermined direction H.

The irradiation starting positions and the irradiation patterns of thelight rays 8 in relation to the respective diffraction lattice areas K1. . . Kn to be formed may be controlled by the PC 24. By theabove-mentioned method, the diffraction lattice row R is formed on therelief formation layer 2. The obtained relief formation material 3 maybe further processed properly to obtain the first image body I-1 of amoving image. The control of light irradiation such as the irradiationpitches, irradiation intensity, and moving speed corresponding to theformation of the respective diffraction lattice areas K1 . . . Kn may becarried out by previously set the respective values for the control andperformed by the PC 24. The formation order of the respectivediffraction lattice areas K1 . . . Kn is optional.

In this embodiment, the sizes of the respective diffraction latticeareas K1. Kn are same, however they may be different by areas. Thepredetermined direction H is not necessarily straight, and can be bentat predetermined angles, spiral, or curved. The diffraction lattice rowR formed in the first image I-1 is not necessarily single, and aplurality of rows may be formed.

Further, a plurality of relief pattern sheets 6 are made ready whileeach of the relief patterns 5 being made different from one another anda plurality of the relief patterns 5 are combined so as to compose onegeneratrix assembly, and the respective generatrices of a plurality ofrelief patterns 5 may be formed on the relief formation layer 2 so as toobserve images corresponding to respective characteristics of each ofthe plurality of relief patterns 5 by combining a plurality of thegeneratrix assemblies.

Accordingly, an image body containing images corresponding to respectivecharacteristics of a plurality of the relief patterns 5 can be obtainedin a single plane. The characteristics of the relief patterns 5 mayinclude images obtained owing to the light interference and thedirections in which the images are observed. One generatrix assembly ispreferably small enough not to be seen with the naked eye and accordingto the invention using light, fine interference fringes can be formed.Therefore, the invention is applicable in the case the kinds of reliefpatterns 5 contained in the generatrix assembly of a predetermined sizeincrease.

Hereinafter, using a second image body I-2 as an image body in whichdifferent images can be observed depending on observation direction whenit is observed from different observation directions, its formationmethod will be described. In the formation method, a relief patternsheet 6 having hologram patterns as the relief patterns 5 will be used.Hereinafter, the relief patterns 5 in this formation method are calledas hologram patterns 5.

In this embodiment, a second image body I-2 in which four type imagesare observed from four observation directions will be described. Asshown in FIG. 8, if the second image body I-2 is divided into divideddivisions D as a plurality of generatrix assemblies, as shown in FIG. 9,the respective divided divisions Dare composed of four generatrixportions P1 to P4. Hereinafter, if it is no need to particularlydistinguish the generatrix portions P1 to P4, they are called simplygeneratrix portions P. The boundaries of the respective divideddivisions D of FIG. 8 and the boundaries of the respective generatrixportions P of FIG. 9 are made visible only for making the explanationeasily understandable and not practically observable lines. Further, itis preferably the divided divisions D are small enough not to beobserved.

Different kind of hologram patterns 5 from each other is formed in therespective generatrix portions P1 to P4 and each of the generatrixportions P1 to P4 functions as a generatrix, so that imagescorresponding to the characteristics of the respective hologram patterns5 can be observed in the respective observation directions. For example,in the observation direction Di1 corresponding to the generatrix portionP1, an image G shown in FIG. 8 can be observed and in the observationdirection Di2 corresponding to the generatrix portion P2, another imagecan be observed. Similarly, with respect to the generatrix portion P3and the generatrix portion P4, an image different from those of othergeneratrix portions can be observed in a different observation directionfrom those of other generatrix portions. Accordingly, to form the secondimage body I-2, first hologram patterns 5 to express the respectivelydifferent images and to have respectively different observationdirections are selected and each of the hologram patterns 5 iscorresponded with each of the generatrix portions P1 to P4 in 1 to 1relation.

Next, the formation method for the second image body I-2 based on thefour type hologram patterns selected in the above-mentioned manner willbe described more practically with reference to FIG. 10. First, a methodfor forming hologram patterns 5 expressing the image G in theobservation direction Di1 in the generatrix portion P1 will bedescribed. A relief pattern sheet 6 having the hologram patterns 5 and arelief formation material 3 are closely attached in the above-mentionedmanner to obtain a laminate 23 and the laminate 23 is set at apredetermined position of the XY stage 22. Next, the photothermalconversion layer 7 is irradiated with light 8 so as to form the hologrampatterns 5 only in the areas B1 . . . B1 of the relief formation layer 2where the generatrix portion P1 is to be formed.

The areas B1 . . . B1 (slanting line part) where the generatrix portionP1 is to be formed are obtained by dividing the pattern formation regionPR into divided divisions D and defining the areas corresponding to thegeneratrix portion P1 in the respective divided divisions D as the areasB1. The pattern formation region PR is the region corresponding to thesecond image body I-2. For example, when the respective areas B1 arescanned at predetermined pitches with light 8, only the hologrampatterns 5 corresponding to the respective areas B1 are formed on therelief formation layer 2 and as a result, the generatrix portion P1functioning as a generatrix of the hologram patterns 5 is formed in theareas B1. The irradiation position and the irradiation pattern of thelight 8 may be previously programmed and controlled by the PC 24.

The respective areas B1 are shown to be big enough to be observed forexplanation easiness but they are actually so small not to be observedwith the naked eye. With respect to other respective generatrix portionsP2 to P4, in the same manner as the case of generatrix portion P1,pattern formation should be carried out in the regions where thegeneratrix portions P of the hologram patterns 5 are to be formed byusing relief pattern sheets 6 of the hologram patterns 5 correspondingto the respective generatrix portions P2 to P4. The irradiation positionand the irradiation patterns of light 8 in relation to each of theregions, where the corresponding generatrix portion P is to be formed,may be controlled by the PC 24. By the above-mentioned method, therespective hologram patterns 5 are formed in all of the generatrixportions P. If necessary, the obtained relief formation material 3 maybe processed further to obtain the second image body I-2.

In this embodiment, the second image body I-2 in which four typeholograms are expressed by dividing the region into four divideddivisions D is formed, however the number of the generatrix portions tobe included in one divided division D is not particularly limited if itis 2 or higher. In this case, the plural kinds of the hologram patterns5 which are equal to the number of the divided generatrix portions areused for the formation. Further, in FIG. 9, the respective hologrampatterns 5 are formed in the entire body of the respective generatrixportions, however depending on the images to be formed in the respectivegeneratrix portions P, the hologram patterns 5 are formed only partiallyin the generatrix portions P in some cases. Also, as the plural reliefpatterns 5, respective diffraction lattice patterns 5 each correspondingto three primary colors are made to correspond to the respectivegeneratrix portions P, so that color hologram in specific observationdirection can be expressed.

Further, as the relief pattern sheet 6 having the relief patterns 5, afirst relief pattern sheet having first relief patterns and a secondrelief pattern sheet 6 having second relief patterns different from thefirst relief patterns are made ready and the first and the second reliefpatterns may be formed in the relief formation layer 2 in such a mannerthat fine regions where the second relief patterns are formed haveshapes so small as not to be observed with the naked eye and assembledin the background region which is formed by using the first reliefpatterns.

Accordingly, it is made possible to obtain an image body in which thebackground region formed by using the first diffraction lattice patternsis observed with the naked eye but the shape of each fine region whichis formed by using the second relief patterns is not recognized with thenaked eye, and the shape is recognized as a point or a line. The fineregions are observed like point or linear patterns on the firstdiffraction lattice patterns with the naked eye and their shapes arerecognized only when they are magnified with a microscope or the like.If the shapes are made to be letters or marks, the obtained image bodycan be used for security means.

Hereinafter, exemplifying a third image body I-3 as the image body inwhich the fine regions are assembled in the background region, theformation method for the image body will be described. In the formationmethod, a relief pattern sheet 6 having diffraction lattice patterns asthe relief patterns 5 is used. Hereinafter, in the formation method, therelief patterns 5 are called as diffraction lattice patterns 5.

The third image body I-3 is composed of the background region BR inwhich first diffraction lattice patterns are formed and a plurality offine regions DR . . . DR seemed to be points assembled in the backgroundregion BR when observed with the naked eye. The respective fine regionsDR looking like only points with the naked eye are formed to be in starshape by the second diffraction lattice patterns different from thefirst diffraction lattice patterns as shown in FIG. 12. The shapes ofthe fine regions DR are recognized only when they are magnified with amicroscope or the like. Hereinafter, the formation method for the thirdimage body I-3 will be described more particularly along with FIG. 13and FIG. 14.

First, as shown in FIG. 13, the first relief pattern sheet 6 having thefirst diffraction lattice patterns 5 to be formed in the backgroundregion BR and a relief formation material 3 are closely attached in theabove-mentioned manner to obtain a laminate 23 and the laminate 23 isset at a predetermined position of a stage XY stage 22. Successively,the photothermal conversion layer 7 is irradiated with light 8 in such amanner that the first diffraction lattice patterns 5 are formed in theregion C1 of the relief formation layer 2 where the background region BRis to be formed.

For example, in the region C1 where the background region BR is to beformed, when the light 8 is moved so as to draw scanning lines SC3 atpredetermined pitches, the first diffraction lattice patterns 5 areformed in the region C1 and accordingly, the background region BR isformed in the region C1. The background region BR may be formed in suchmatter that formation of the first diffraction lattice patterns 5 isavoided in the region where formation of the second diffraction latticepatterns 5 is carried out. The irradiation position and the irradiationpatterns of the light 8 are controlled by the PC 24. The scanning linesSC3 of the light are shown only for the explanation and they are notactually observed with the naked eye.

Next, the first relief pattern sheet 6 is separated from the reliefformation material 3 and as shown in FIG. 14, the second relief patternsheet 6 having the second diffraction lattice patterns 5 and the reliefformation material 3 are closely attached to each other in theabove-mentioned manner to obtain a laminate 23 and the laminate 23 isput at a predetermined position of the XY stage 22. Successively, thephotothermal conversion layer 7 is irradiated with light 8 in such amanner that the second diffraction lattice patterns 5 are formed in theregions C2 . . . C2 where the fine regions BR of the relief formationlayer 2 are to be formed.

For example, if light 8 is scanned at predetermined pitches in oneregion C2, the second diffraction lattice patterns 5 are formed in theregion C2 and as a result, fine regions DR are formed in the regionwhere they are to be formed. The irradiation position and theirradiation pattern of the light 8 may be controlled by the PC 24. Eachregion C2 is shown with a size observed with the naked eye forexplanation convenience, but it does not have a size large enough to berecognized. Further, the boundary lines of each region C2 are also shownfor explanation convenience, but they are not observable with eye. Bythe above-mentioned method, the background region BR and fine regions DRare formed in the relief formation layer 2. The third image body I-3 canbe obtained by processing properly the obtained relief formationmaterial 3.

In this embodiment, the shapes formed by the second diffraction latticepatterns have star form, but the shape is not limited to the star, andcan be letters or designed patters. The respective relief patterns to beused for the background region BR and the fine regions DR should bedifferent and are not limited to the diffraction lattice patterns.

In this embodiment, the laminate 23 is set on the XY stage at the timeof formation of the first to the third image bodies I-1 to I-3, but itmay be attached to a side face of a drum by vacuum adsorption. In such acase, the perpendicular direction is controlled by rotation of the drumand the horizontal direction may be controlled by moving the laser head21 of the light 8 in the horizontal direction. In this embodiment,although the photothermal conversion layer 7 is formed independently, ifa substance increasing the photothermal conversion efficiency is addedto any layer of either the relief formation material 3 or the reliefpattern sheet 6, it is not necessarily required to form the photothermalconversion layer 7.

If relief pattern sheets 6 having the first image body I-1, the secondimage body I-2, or the third image body I-3 obtained in theabove-mentioned formation method as a master hologram is used andirradiation of the light 8 is controlled so as to form all of theconcavo-convex patterns of the respective image bodies, the respectiveimage bodies can easily be copied.

Next, an embodiment of execution of hologram copying method and methodfor producing an optical diffraction structure according to theinvention will be described. FIG. 15 shows an optical diffractionstructure production apparatus to be used in the embodiment. In theoptical diffraction structure production apparatus, a laser irradiationapparatus 100 for irradiating somewhere with IR laser L as energy beam,a drum apparatus 102 for holding a master hologram, and a transportationapparatus 103 are connected to a control apparatus 104 for controllingthe operation of the above-mentioned apparatuses through drivers 105,106, and 107 respectively.

The drum apparatus 102 is provided with a column type drum 102 a and amotor 102 c for rotating the drum 102 a on the axis 102 b in thedirection Q. Numberless small holes are formed in the entire outercircumferential face of the drum 102 a and the air in the inside of thedrum 102 a is sucked by a suction pump not illustrated, so that negativepressure is generated in the inside of the drum 102 a to attach a masterhologram 110 and a film 111 for hologram formation to the surface of thedrum 102 a. The respective structures of the master hologram 110 and thefilm 111 for hologram formation will be described later.

The transportation apparatus 103 is provided with a transportation part103 and a motor 103 c for moving the transportation part 103 a in thedirection parallel to the axial direction of the drum 102 a, that is inthe direction shown as the arrow F, by a rail 1 103 b. Since the laserirradiation apparatus 100 is set on the transportation part 103 a, alongwith the transportation of the transportation part 103 a, the laserirradiation apparatus 100 can move in parallel to the side face of thedrum 102 a.

The laser irradiation apparatus 100 irradiates the master hologram 110attached to the side face of the drum 102 a with IR laser L. Theirradiation range of the IR laser L in the master hologram 110 can beshifted by the parallel movement of the laser irradiation apparatus 100by the above-mentioned transportation apparatus 103 and rotation of thedrum 102 a.

The control apparatus 104 is composed to be a computer comprising a CPUand various peripheral circuits such RAM and ROM necessary for theoperation of CPU and is employed to control the operations of theabove-mentioned laser irradiation apparatus 100, drum apparatus 102, andtransportation apparatus 103 according to previously installed programs.Accordingly, shift of the irradiation range of the IR laser L with whichthe master hologram 110 is irradiated by the laser irradiation apparatus100 is controlled by the control apparatus 104.

Next, the structures of the master hologram 110 and the film 11 forhologram formation will be described along with FIG. 16. FIG. 16 showsthe state that master hologram 110 and the film 111 for forming hologramto be used in this embodiment are laminated on the outer circumferenceof the drum 102 a. As shown in FIG. 16, the master hologram 110 isprovided with a hologram layer 120 in which the interference fringes areformed in concavo-convex form and a base substrate layer 121 ofpolyethylene terephthalate.

The master hologram 110 can be produced by a conventionally knownmethod. The hologram to be used for the hologram layer 120 may be thosewhich can record hologram information by the concavo-convex form in thematerial surface and are applicable for a conventional method forcopying hologram by using a thermoplastic resin. Practically, hologramsbased on the Frenel hologram, Fourier transform hologram, Fraunhoferhologram; and the holograms utilizing their principles, such as imagehologram, holographic stereogram, and holographic diffraction latticecan be used. In place of the master hologram 110, a diffraction latticehaving the concavo-convex patterns evenly formed therein may be used andin this case, the lattice patterns of the diffraction lattice aretransferred to the film 111 for forming hologram.

On the other hand, the film 111 for forming hologram is composed bylayering a primer layer 123 and a fusion layer 124 on the base substratelayer 122 of polyethylene terephthalate. The fusion layer 124 compriseswax, a thermoplastic resin, and a high heat conversion material as asubstance for increasing the conversion efficiency from light energy ofIR laser to heat energy. The thermoplastic resin and wax composing thefusion layer 124 may be those which are solid state at a normaltemperature. The primer layer 123 functions as a primer for sticking thebase substrate layer 122 and the fusion layer 124 to each other.

The principle of the transformation of the concavo-convex form of thehologram layer 120 to the fusion layer 124 by IR laser L will bedescribed with reference to FIG. 17. In FIG. 17, the master hologram 110and the film 111 for forming hologram are attached to the outercircumference of the drum 102 a as described above. the master hologram110 and the film 111 for forming hologram layered each other isirradiated from the base substrate layer 121 side with the IR laser Lmoving in the direction shown as the arrow C.

In the fusion layer 124, an irradiation range W1 of the fusion layer 124is heated by the heat of the IR laser L. When the temperature of theirradiation range W1 of the fusion layer 124 reaches the fusing point,the fusion layer 124 in the range is fused and the interference fringesof the hologram layer 120 in the irradiation range W1 are transferred tothe fusion layer 124. Next, the IR laser L is shifted to an irradiationrange W2. FIG. 17 shows the state that the interference fringes in theirradiation range W1 are transferred to the fusion layer 124 and the IRlaser is shifted to the irradiation range W2.

When the irradiation range of the IR laser L is shifted, the temperaturein the transferred range W1 of the fusion layer 124 decreases without aparticular cooling process and the fused fusion layer 124 becomes cured.On the other hand, when the new irradiation range W2 in the fusion layer124 is heated and the temperature of the irradiation range W2 of thefusion layer 124 reaches the fusing point, the fusion layer 124 in therange is fused and the interference fringes of the hologram layer 120 inthe irradiation range W2 are transferred to the fusion layer 124.Thereafter, similarly, the interference fringes in the ranges which isirradiated with the IR laser L are successively transferred to thefusion layer 124.

Next, the method for producing an optical diffraction structure of theinvention will be described practically with reference to FIGS. 18A,18B, 19A, and 19B. FIG. 19B shows an optical diffraction structure inwhich the interference fringes for producing a hologram image 130 arecombined with a drawn image 133 with a predetermined form drawn by adiffraction lattice. Hereinafter, the method for producing an opticaldiffraction structure by the invention will be described. The method forproducing an optical diffraction structure of the invention comprises ahologram copying process and a diffraction lattice drawing process. Theorder of these two processes is optional. In this embodiment, thecopying process is carried out previously and the drawing process later.

First, the copying process will be described. FIG. 18A shows a masterhologram 110 in which the interference fringes for producing thehologram image 130 to be copied on the film 111 for forming hologram areprovided. The object range to be copied in this embodiment is the entireinterference fringes formed in the master hologram 110. The film 111 forforming hologram is stuck to the outer circumferential face of the drum102 a of the optical diffraction structure production apparatus (FIG.15) and the master hologram 110 is layered thereon. As described above,negative pressure is generated in the inside of the drum 102 a, so thatthe pressure in the inside of the drum 102 a is lower than the pressurein the outside and therefore, the film 111 for forming hologram and themaster hologram 110 layered on the drum 102 a are attracted to the outercircumference of the drum 102 a. In FIG. 18B, the master hologram 110 issmaller than the film 111 for forming hologram, however it is sufficientif the film 111 for forming hologram has the size such that the objectrange to be copied of the master hologram 11 can be transferred to thefilm 11 for forming hologram.

Next, as shown in FIG. 18B, as tracing the interference fringes of themaster hologram 110, the master hologram 110 is irradiated with IR laserL. In the operation, the irradiation position of the IR laser L iscontrolled by the program taken in the control apparatus 104. That is,the operation is executed by controlling the operations of drumapparatus 102 and the transportation apparatus 103. With the shift ofthe irradiation position, the interference fringes for producing thehologram image 130 are transferred to the fusion layer 124 of the film111 for forming hologram. In such a manner, since the master hologram110 in which the hologram image 130 is previously formed is easilytransferred by IR laser L, even if the hologram image 130 iscomplicated, the hologram image can be copied easily by IR laser Lwithin a short time.

Next, the drawing process will be described. In place of the masterhologram 110, a diffraction lattice 132 is layered on the film 111 forforming hologram to which the hologram image 130 has been transferred.The diffraction lattice 132 has constant concavo-convex patterns formedevenly. In this embodiment, the diffraction lattice 132 having thelayered structure similarly to the master hologram 110 and havingconstant concavo-convex patterns formed evenly in the layercorresponding to the hologram layer 120 is used. Next, when theirradiation starting position of the IR laser L is set at a point wherethe drawing image 133 is to be drawn and an instruction of the image tobe drawn is given to the control apparatus 104, the operations of thedrum apparatus 102 and the transportation apparatus 103 are controlledaccording to the program taken in the control apparatus 104 to shift theirradiation position. Further, the irradiation of the IR laser L isrepeatedly turned on or off so as to draw the drawing image 133. FIG.19A shows the state that the drawing image 133 is drawn by the IR laserL. The concavo-convex patterns of the diffraction lattice to betransferred in the drawing process are not a hologram in a strictdefinition, however the film 111 for forming hologram to be used in thecopying process is used as it is.

In the above-mentioned copying process and drawing process, as shown inFIG. 19B, the optical diffraction structure in which the hologram image130 and the drawing image 133 are combined on the film 111 for forminghologram can be produced. Accordingly, it is made easy to produce ahologram synthesized employee badge comprising the hologram image 130 asa company mark and the drawing image 133 as the face of the employee, orto produce hologram synthesized photograph having cubic background ifthe hologram image 130 is the cubic background and the drawing image 133is a face of a man.

The following description is a method for producing an opticaldiffraction structure having deep depth feeling by making anotherdiffraction lattice 132 ready which has a focused image of theinterference fringes at a position different from the focused imageposition of the interference fringes of the diffraction lattice 132 inthe depth direction and transferring the interference fringes of theanother diffraction lattice 132 to the fusion layer 124. Normally,though a dry plate, which is an object to be photographed, is set at aposition where the interference fringes are focused to form an image(hereinafter, referred to as a focusing position) in the case thediffraction lattice is produced by interference fringes of laser beamwith 2 or more luminous fluxes, the another diffraction lattice 132 canbe obtained by photographing the dry plate at a position shifted in thehorizontal direction from the focusing position (e.g. the positionshifted from the focusing position by −4 mm, −2 mm, +2 mm or +4 mm inthe horizontal direction).

For example, the another diffraction lattice 132 is produced by settingthe dry plate at the position shifted from the focusing position by −4mm and by the procedure same as that for drawing the drawing image 133as the first predetermined shape by the diffraction lattice 132 in theabove-mentioned drawing process, the second predetermined shape to bethe background of the drawing image 133 is drawn on the film 111 forforming hologram by the another diffraction lattice 132. Accordingly,when the hologram image 130 is made as a company mark and the drawingimage 133 drawn by the diffraction lattice 132 produced by theabove-mentioned normal production method is made as a face of anemployee, an apparent distance can be generated between the face of theemployee and the background and thus a cubic image expression can beformed in the produced optical diffraction structure.

The hologram copying method and the method for producing an opticaldiffraction structure for the invention are not limited to theabove-mentioned embodiment and may be carried out in variously modifiedstates. For example r in the above-mentioned embodiment, IR laser L isused as the energy beam, electron beam and x-ray may be used. In such acase, a film 111 for forming hologram having a fusion layer 124generating heat by using the energy beam may be used properly. The speedof the shifting the irradiation range of the IR laser L, electron beamor the like may properly be set to a proper speed at which the hologramand the diffraction lattice can be transferred without any particularcooling process, on the basis of the composing materials of the masterhologram 110 and the film 111 for forming hologram and the irradiationrange.

Other than the above-mentioned polyethylene terephthalate, any materialwith which the invention is performed can be used for the base substratelayer 121 of the master hologram 110 and the base substrate layer 122 ofthe film 111 for forming hologram. The mixing ratio of the substancescomposing the respective layers is properly changeable to the extentthat the invention can be executed with the constitution substances.Further, in this embodiment, the master hologram 110 and the film 111for forming hologram are layered by generating the negative pressureinside of the drum 102 a, the mutually layered master hologram 110 andfilm 111 for forming hologram may be pressurized from both sides. Themaster holograms 110 and diffraction lattices 132 are made ready for therespective colors R, G, and B and copying may be carried out for therespective colors.

Next, an embodiment of the method for copying an optical diffractionstructure for the invention will be described. In this embodiment, usingthe optical diffraction structure copying apparatus shown in FIG. 15,the concavo-convex patterns of the optical diffraction structuremaster-hologram having the same constitution as that of the masterhologram 110 shown in FIG. 16 are transferred to a transfer mediumhaving the same constitution as that of the film 111 for forminghologram. Accordingly, descriptions relevant to the optical diffractionstructure copying apparatus, the master hologram 110, and the film 111for forming hologram in this embodiment are as described and therefore,they are not repeated.

In the hologram layer 120 of the master hologram 110 in the embodiment,as shown in FIG. 20, interference fringes for producing letters “DNP” ashologram images are formed. The object region for copying is the entiremaster hologram 110.

The copying method for the optical diffraction structure of theinvention comprises a first transfer process and a second transferprocess. First, the first transfer process will be described. The masterhologram 110 and the film 111 for forming hologram are layered and seton the drum 102 a while the film 111 for forming hologram being setunder. As described above, the master hologram 110 and the film 111 forforming hologram are attracted to and fixed in the side face of the drum102 a by the negative pressure generated in the inside of the drum 102a. Next, The master hologram 110 is irradiated from the laserirradiation apparatus 100 with IR laser L1 in the first transferprocess.

As shown in FIG. 21A, the master hologram 110 is irradiated with the IRlaser L1 so as to draw straight scanning lines S1 . . . Sn (hereinafter,in the case the lines are not necessary to be specially distinguished,referred simply to as “scanning lines S”) in a lengthwise direction as aconstant direction. The scanning lines S are drawn by shifting theirradiation range of the IR laser L1. FIG. 21A shows the state that thescanning lines S1 to Sn are already drawn and the scanning line Sn+1 isbeing drawn.

When the fusion layer 124 is irradiated with the IR laser L1, the lightenergy of the IR laser L1 is converted into heat energy to heat theirradiation range. When the temperature of the irradiation range reachesthe fusing point of the fusion layer 24, the irradiation range is fusedand the interference fringes overlaid in the fused part are transferred.Accordingly, as the scanning lines S are drawn by the IR laser L1, thatis, the irradiation range is shifted, the interference fringes in theirradiation range of the master hologram 110 are successivelytransferred to the fusion layer 124 of the film 111 for forminghologram. In this embodiment, the line width and the pitches of thescanning lines S are previously set to be 65 μm and 60 μm, respectively,in the optical diffraction structure copying apparatus and the startingposition and the finishing position of the respective scanning lines Sare controlled based on the program taken in the control apparatus 104.When the control apparatus 104 judges that the entire body of the masterhologram 110 is scanned by the IR laser L1, the first transfer processis finished. In FIG. 21A, the scanning lines S are shown as visiblelines for explanation convenience, however the scanning lines are tracesof the irradiation ranges of the moving IR laser L1 and no visible lineis actually drawn in the master hologram 110.

FIG. 21B shows a cross-sectional view of the obtained film 111 forforming hologram on completion of the first transfer process along theline M. As shown in FIG. 21B, cyclic concavo-convex form is formed inthe fusion layer 124. One rising part corresponds to the line width ofone scanning line S and the highest part H1 is the center part of theirradiation range of the IR laser L1 and the lowest parts E1 areboundary parts of the irradiation range of the IR laser L1. Since theenergy dose of the IR laser L1 in the center part of the irradiationrange is higher than those in its boundary parts, the fusion layer 124in the irradiation range is easy to be fused and the fusion layer 124 inthe boundary parts are relatively hard to be fused. Accordingly, in thefusion layer 124 pressurized from the upper side by the master hologram110, the part easy to be fused is easy to rise and the shape shown inFIG. 2B can be formed by drawing a plurality of scanning lines S inparallel.

Next, the second transfer process will be described. In the secondtransfer process, the master hologram 110 and the film 111 for forminghologram may be as they are at the time of finishing the first transferprocess. In the second transfer process, the boundary parts of thescanning lines S drawn in the first transfer process are irradiated withIR laser L2 to draw scanning lines SS1 . . . SSn (hereinafter, in thecase the lines are not necessary to be specially distinguished, referredsimply to as “scanning lines SS”) shown as dotted lines along with thescanning lines S. The scanning lines SS are drawn by shifting theirradiation range of the IR laser L2. FIG. 22A shows the state that thescanning lines SS1 . . . SSn are already drawn by the IR laser L2 on themaster hologram 110 and the scanning line SSn+1 is being drawn. Theenergy dose of the IR laser L2 is determined relatively to the energydose of the IR laser L1 and it may be in a range of 0.3 to 1 time asmuch as that of the IR laser L1. In this embodiment, the energy dose ofthe IR laser L2 is set so as to adjust the line width of the scanninglines SS to be 35 μm.

As the scanning lines SS are drawn, that is, with the shift of theirradiation range of the IR laser L2, because of the same reason as theprinciple described above, the interference fringes in the irradiationrange of the master hologram 110 are successively transferred. Thepitches and the line width of the scanning lines SS are previously setand the starting position and the finishing position of the respectivescanning lines SS are controlled based on the program taken in thecontrol apparatus 104. When the control apparatus 104 judges that all ofthe boundary parts of the scanning lines S are scanned by the IR laserL2, the second transfer process is finished. Although the scanning linesSS are drawn as visible dotted lines for explanation convenience in FIG.22A, the scanning lines SS are traces of the irradiation range of themoving IR laser L2 and no visible dotted line is drawn actually on themaster hologram 110.

FIG. 22B shows a cross-sectional view of the obtained film 111 forforming hologram on completion of the second transfer process along theline M. As shown in FIG. 22B, because of the same reason as that in thefirst transfer process, cyclic concavo-convex form drawn with dottedline is formed in the boundary parts of the scanning lines S. One risingpart corresponds to the line width of one scanning line SS and thehighest part H2 is the center part of the irradiation range of the IRlaser L2 and the lowest parts E2 are boundary parts of the irradiationrange of the IR laser L2. The highest part H2 is formed in the positionof the lower parts E1 generated in the first transfer process, so thatthe height difference in the surface of the fusion layer 124 caused bythe first transfer process can be amended. Accordingly, the surface ofthe fusion layer 124 of the film 111 for forming hologram obtained afterthe second transfer process is provided with improved flatness than thesurface of the fusion layer 124 of the film 111 for forming hologramobtained after the first transfer process.

The method for copying an optical diffraction structure for theinvention is not limited to the above-mentioned embodiment and can beperformed in various embodiments. For example, in this embodiment,although the method for copying one master hologram 110 to one film 111for forming hologram is described, master holograms 110 . . . 110 toexpress a plurality of hologram images or master holograms 110 . . . 110of diffraction lattices may be combined and according to the copyingmethod as described above, they may be copied to one film 111 forforming hologram. In this case, if the film 111 for forming hologram inwhich all of the master holograms 110 . . . 110 are copied is copied toan easily adhesive transparent PET film by the 2P copying method, byusing this PET film as the hologram original fome, it is easy to copythe hologram to express a plurality of hologram images.

Further, from the holograms and diffraction lattice patterns arranged bythe invention, other holograms and diffraction lattice patterns can berepeatedly arranged by the method for the invention. In this case, whenthe scanning pitches employed at the initial arrangement are differentfrom the scanning pitches employed at the second arrangement, forexample, the scanning pitches of the first arrangement are adjusted tobe 80 μm and the scanning pitches of the second arrangement are adjustedto be 60 μm, if not executing the flatness improvement by the invention,vertical stripes (moires) are generated by the pitch of 240 μm which isleast common multiple of 60 and 80. By the flatness improvement of theinvention, the vertical stripe (moires) formation can be prevented andtherefore, it is not necessary that the scanning pitches of the secondarrangement are not equal to the scanning pitches of the firstarrangement. That is, there is an advantageous that the scanning pitchesare set freely.

The energy dose of the IR laser L1 in the first transfer process may beset properly based on the raw materials and the depth of the hologramlayer 120 and the fusion layer 124. The energy does of the IR laser L2may be set higher than that of the IR laser L1. The energy doses of therespective IR laser beams L1 and L2 may be adjusted so as to obtain theflatness of the surface of the fusion layer 124 of the finally obtainedfilm 111 for forming hologram. Also, the shifting speeds of the IR laserL1 and IR laser L2 may be set properly based on the raw materials of thefusion layer 124 and the depth of the interference fringes in the fusionlayer 124 and the hologram layer 120 so as to heat the fusion layer 124to the fuse point and then spontaneously cool the fusion layer 124quickly.

In this embodiment, the copying method for obtaining the opticaldiffraction structure by two time transferring processes in total: thefirst transfer process and the second transfer process: is explained,and a third transfer process for irradiating the boundary parts of thescanning lines SS of the second transfer process with IR laser havingsmaller energy dose than that of the IR laser L2 may be further added.Thus, transfer processes similar to the second transfer process may becarried out without any limit in the times of repeating the processes.

EXAMPLE 1

A photothermal conversion layer and UV curable resin layer(not-yet-cured but solid and thermoplastic) were successively formed onthe surface of a substrate of a polyethylene terephthalate (PET) sheet.The surface of the not-yet-cured UV curable resin layer and a reliefpattern sheet (OVD sheet) in which the diffraction lattice pattern (OVD)as a master hologram was grooved were closely attached by vacuumadsorption method to obtain a laminate.

Next, using semiconductor laser with wavelength of 808.5 nm as thelaser, the above-mentioned laminate was set on XY stage while thesubstrate side being set in the laser irradiation side and the XY stageshown in FIG. 3 was moved to the starting point for drawing. Whendrawing image was instructed from PC, based on the image drawingprogram, the XY stage was moved according to the output image pattern soas to move the laser irradiation position and at the same time theirradiation of the IR laser was repeatedly turned on and off to drawpredetermined patterns. The XY stage was moved at 20 mm/sec speed andthe laser was beamed so as to adjust the spot diameter 72 μm, the laseroutput 0.935 W, irradiation energy per 1 dot (diameter 72 μm)9,350×(0.072/20)=33.7 mJ, and the irradiation dose per unit length33.7×(1/0.072)=468 mJ. As a result, the part of the photothermalconversion layer to which the IR laser was beamed was heated and theUV-curable resin layer in the part brought into contact with thephotothermal conversion layer was fused and the concavo-convex patternform corresponding to the concavo-convex form of the OVD sheet of therelief pattern sheet, brought into contact with the UV-curable resinlayer was formed in the UV-curable resin layer. After the IR laserirradiation, the relief pattern sheet was separated to obtain aconcavo-convex pattern formed body where the concavo-convex pattern ofthe diffraction lattice was formed on the surface of the substratesheet. The photothermal conversion layer, the UV-curable resin layer,and the relief pattern sheet were produced by the following methods.

[Formation Method for Photothermal Conversion Layer]

The following coating solution composition was produced and applied tothe surface of a PET sheet by a gravure coating method (coating amount:0.5 g/m²).

[Coating Solution Composition for Photothermal Conversion Layer: Ratioon the Basis of Parts by Weight]

Carbon black (Miyoshi Kagaku: #258) 1,

Binder resin (polyester resin, TOYOBO Vylon 200) 1,

UV curing agent (Takenate A10: Mitsui Takeda Chemicals, Inc.) 0.1, and

Solvent (MEK/toluene=1/1) 8.

[Formation Method for UV-Curable Resin Layer]

The composition with the following mixing ratios was diluted with methylethyl ketone (MEK) r and the solid matter was adjusted in thecomposition to be 50% to obtain an ink, and the ink was applied to theabove-mentioned photothermal conversion layer by gravure coating method(coating amount: 2 g/m²).

[Composition of UV-Curable Resin Layer: Ratio on the Basis of Parts byWeight]

Urethane-modified acrylate (A) 100,

Silicone (trimethylsiloxysilicic acid-containing methylpolysiloxane,trade name: KF-7312, manufactured by Shin-Etsu Chemical Co., Ltd.) 1,

Polyfunctional urethane acrylate (trade name: Ultraviolet UV-1700B,manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.) 25,and

Photopolymerization initiator (trade name: Irgacure 907, manufactured byChiba Speciality Chemicals) 5.

The above-mentioned urethane modified-acrylate (A) was produced by thefollowing method.

A four-neck flask having 2 L capacity equipped with a cooling apparatus,a titration funnel, and a thermometer was loaded with toluene 40 g andmethyl ethyl ketone (MEK) 40 g together with an azo type initiator and amixed solution of 2-hydroxyethyl methacrylate (HEMA) 24.6 g, methylmethacrylate (MMA) 73.7 g, dicyclopentenyloxyethyl methacrylate 24.6 g,toluene 20 g, and MEK 20 g was dropwise added through the titrationfunnel in about 2 hours while the reaction was carried out at thetemperature of 100 to 110° C. for 8 hours and then the resultingreaction solution was cooled to a room temperature. The cooled solutionwas further mixed with a mixed solution of 2-isocyanate ethylmethacrylate (Karenzu MOI, manufactured by Showa Denko K.K.) 27.8 g,toluene 20 g, and MEK 20 g and using dibutyl tin laurate as a catalyst,addition reaction was carried out. The reaction product was subjected toIR analysis and when it was confirmed that the absorption peak of theisocyanate group at 2,200 cm⁻¹ disappeared, the reaction was finished.The obtained urethane-modified acrylate solution was found containingnon-volatile components 41.0% and having a molecular weight of 30,000measured by GPC analysis of the acrylate (solvent THF, conversion on thebasis of standardized polystyrenes) and an average number of doublebonds in one polymer molecule 13.0% by mole.

[Production Method for Relief Pattern Sheet]

The relief pattern sheet was produced by 2P method. A UV-curable resin(UV-SEL clear-OP vanish, manufactured by INCTEC INC.) was dropwisetitrated to an easily adhesive PET sheet and the sheet was laminated ona diffraction lattice pattern resin master-hologram and UV ray wastemporarily beamed and after that, the diffraction lattice pattern resinmaster-hologram was separated and UV ray was re-beamed to thetemporarily cured relief patterns corresponding to the diffractionlattice patterns formed on the surface of the easily adhesive PET sheetto actually cure the relief patterns.

EXAMPLE 2

A UV curable resin layer (not-yet-cured but solid and thermoplastic) wasformed on the surface of a substrate of a polyethylene terephthalate(PET) sheet, and the surface of the not-yet-cured UV curable resin layerand a relief pattern sheet (OVD sheet) in which the diffraction latticepattern (OVD) as a master hologram was grooved and the photothermalconversion layer was formed were closely attached by vacuum adsorptionmethod to obtain a laminate and the laminate was irradiated with laserbeam in the same manner as described in Example 1 to form theconcavo-convex pattern form corresponding to the concavo-convex form ofthe OVD sheet of the relief pattern sheet on the UV-curable resin layer,and a concavo-convex pattern formed body was obtained, in which theconcavo-convex pattern of the diffraction lattice was formed on thesurface of the substrate sheet. The materials, laser drawing method andapparatus same as those employed in Example 1 were used except that thephotothermal conversion layer was formed in the relief pattern sheet.

[Production Method for Relief Pattern Sheet]

First, the photothermal conversion layer was formed in the easilyadhesive PET sheet. The photothermal conversion layer was formed in thesame method by using the same composition as the coating composition inExample 1. Next, the UV-curable resin for a forme material (UV-SELclear-OP vanish, manufactured by INCTEC INC.) was dropwise titrated tothe photothermal conversion layer and the resulting sheet was laminatedon the resin master-hologram having the diffraction lattice patterns; UVrays were temporarily beamed; and then the resin master-hologram havingthe diffraction lattice patterns was separated and UV rays werere-beamed to actually cure the relief patterns to obtain the sheet onwhich the PET sheet, the photothermal conversion layer and the reliefpatterns were successively formed.

1. A method for forming fine concavo-convex patterns by using a relief formation material having a relief formation layer composed of a resin having thermoplasticity and a relief pattern sheet having on a surface thereof relief patterns corresponding to fine concavo-convex patterns of a master hologram, wherein a photothermal conversion layer is formed in the relief formation material or the relief pattern sheet; the photothermal conversion layer is irradiated with light to make the photothermal conversion layer generate heat in the state that the relief formation material and the relief pattern sheet are brought into contact with each other in such a manner that the relief formation layer is brought into contact with the relief patterns; and the fine concavo-convex patterns of the master hologram corresponding to the relief patterns are formed on the relief formation layer.
 2. The method for forming fine concavo-convex patterns according to claim 1, wherein the photothermal conversion layer is formed in the relief pattern sheet and the relief pattern sheet side is irradiated with the light.
 3. The method for forming fine concavo-convex patterns according to claim 1, wherein the photothermal conversion layer is formed in the relief formation material.
 4. The method for forming fine concavo-convex patterns according to claim 1, wherein the relief formation layer is composed of an ionizing radiation-curable resin having thermoplasticity.
 5. The method for forming fine concavo-convex patterns according to claim 1, wherein the relief formation material and the relief pattern sheet are closely attached to each other by vacuum adsorption. 